PYQ Relevance:[UPSC 2022] Discuss global warming and mention its effects on the global climate. Explain the control measures to bring down the level of greenhouse gases which cause global warming, in the light of the Kyoto Protocol, 1997. Linkage: SO2 as “one of the major greenhouse gases that cause global warming”. Flue Gas Desulphurisation (FGD) units are designed specifically to remove SO2 emissions from the combustion of fossil fuels. Therefore, FGD units serve as a direct “control measure to bring down the level of greenhouse gases” as addressed by the question. |
Mentor’s Comment: India’s top science advisory group has suggested ending the 2015 rule that made it compulsory for all coal-based power plants to install Flue Gas Desulphurisation (FGD) units. This has raised serious concerns because FGDs are key to reducing sulphur dioxide (SO₂) pollution, which causes 15% of India’s PM2.5 levels and leads to breathing problems, environmental damage, and climate change. Although installing FGDs is expensive (₹1.2 crore per MW), experts warn that dropping the plan could harm public health and clean air efforts. Worryingly, only 39 of 537 plants have installed FGDs, and deadlines keep getting pushed back.
Today’s editorial focuses on the analysis of the installation of the Flue Gas Desulphurisation (FGD) units in a thermal power plant. This content is very relevant to GS Paper III (Environment, Science and Technology) Mains.
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Let’s learn!
Why in the News?
A group of experts, led by Principal Scientific Advisor Ajay Sood, has recently suggested that India should cancel the 10-year-old rule that requires all coal-based thermal power plants to install Flue Gas Desulphurisation (FGD) units.
Why India should cancel the 10-Year-Old Rule (2015 FGD Mandate)?
- High Installation Cost Burden: Installing FGD units costs around ₹1.2 crore per MW, which can significantly raise power generation costs and electricity tariffs. Eg: For 97,000 MW of new capacity, the cost would be about ₹97,000 crore, making power less affordable.
- Delayed and Poor Implementation: Despite the 2015 rule, compliance has been dismal—only 39 out of 537 plants had FGDs installed by 2025. Eg: Repeated deadline extensions (up to 2029) show lack of feasibility and institutional capacity.
- Limited Local Air Quality Impact in Some Areas: In certain regions, the contribution of SO₂ emissions from TPPs to PM2.5 levels is relatively small. Eg: In Delhi, most air pollution comes from other sources like vehicles and construction, so FGDs at distant plants may offer minimal benefit.
What is a Flue Gas Desulphurisation (FGD) unit?
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How does it reduce SO₂ emissions from thermal power plants?
- Chemical Neutralisation Reaction: FGD units use alkaline substances like limestone or lime to react with acidic SO₂ in flue gas, converting it into stable, non-toxic compounds. Eg: In wet limestone FGD, SO₂ reacts with limestone slurry to form gypsum (CaSO₄·2H₂O), a harmless industrial byproduct.
- Efficient Scrubbing Techniques: Technologies like wet scrubbers or dry sorbent injection physically remove SO₂ from exhaust gases before release into the atmosphere. Eg: Dry sorbent injection sprays powdered lime into the flue gas stream, which binds with SO₂ and is later captured by filters.
- Controlled Emission Discharge: FGD ensures that the treated flue gas released into the environment has significantly lower SO₂ levels, complying with environmental norms. Eg: Power plants near coasts use sea water FGD, where sea water absorbs SO₂ and is then treated before being discharged safely.
Why are SO₂ emissions harmful?
- Respiratory and Health Issues: Sulphur dioxide (SO₂) irritates the respiratory system, causing problems like asthma, bronchitis, and lung damage, especially in children and the elderly. Eg: Studies in urban industrial areas show a direct link between SO₂ exposure and increased hospital admissions for respiratory illnesses.
- Formation of Secondary Particulate Matter (PM2.5): SO₂ reacts in the atmosphere to form fine particulate matter (PM2.5), which can penetrate deep into lungs and enter the bloodstream, posing serious health risks. Eg: According to studies, 80% of PM2.5 from coal combustion is due to secondary particles formed from SO₂.
- Contribution to Acid Rain: SO₂ combines with water vapor in the atmosphere to form sulphuric acid, leading to acid rain that damages soil, crops, forests, and aquatic ecosystems. Eg: Regions near coal-fired plants have reported acidic lakes and damaged crops due to acid rain deposition.
- Environmental Degradation: High SO₂ levels can corrode buildings, especially monuments made of limestone or marble, and degrade overall air and water quality. Eg: The Taj Mahal has shown signs of yellowing, partly attributed to SO₂-related pollution.
- Climate and Visibility Impact: Though SO₂ itself is not a greenhouse gas, it leads to formation of aerosols, affecting cloud formation, reducing visibility, and causing climate imbalance. Eg: In industrial belts, hazy skies and temperature variations are linked to SO₂-derived aerosols.
What is the status of FGD installation in India (2025)?
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Way forward:
- Prioritised FGD Installation: Expedite FGD implementation in high-emission and densely populated zones to balance cost and health impact.
- Policy and Financial Support: Provide targeted subsidies or incentives to TPPs and integrate FGD costs into long-term tariff planning for smoother adoption.
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